In the past few years, wall heat insulation materials have had significant developments which can conserve materials, while improving the heat insulation properties of the walls, saving energy, and decreasing environmental pollution. Lightweight ceramic heat insulation plates are a type of special ceramic heat insulation plate with low firing temperatures, having large amounts of uniform pores and bulk densities ranging from 0.6-1.0 g/cm3. Besides the benefit of maintaining the durability and fire-proofing properties of traditional ceramics, lightweight ceramic heat insulation plates also have the superior characteristics of being light, heat-insulating, and sound-insulating.
At present, the primary methods for making foamed ceramics (porous ceramics) are a powder green body foaming method and a slurry foaming method, which usually utilize foaming agents and large amounts of raw mineral materials. Because these techniques are complicated, the firing temperatures are high, the costs are relatively high, and it is not easy to continuously make foamed ceramics (porous ceramics) of a large size, thus limiting the applications thereof.
Furthermore, in the past few years, the ceramic industry has been growing greatly, and ceramic waste has been generated in larger and larger quantities, the disposal of which utilizes land and increases the powder quantity in the local air. The landfills utilize considerable manpower and material resources and pollute underground water. The generated ceramic waste not only exerts a huge pressure on the environments of cities, but also limits the economic development of the cities and limits the long-term development of the ceramic industry. Turning the waste into an asset is a focus of concern of both ceramic production companies and the whole of society. Therefore, investigating low-cost lightweight ceramic heat insulation plates utilizing ceramic waste has a significant impact on the improvement of the comprehensive energy efficiency of construction, the comprehensive utilization rate of mineral resources, and the long-term development of the ceramic industry.
CN101186519B discloses a method for making porous ceramic materials, utilizing ceramic waste and polished tile waste as raw materials, adding clay, high temperature sand, and low temperature sand, adding water for wet ball milling, pressurizing into green body ceramic tiles at 8 MPa after drying, and heating at 1140° C. for 100 minutes in a ceramic roller kiln to thereby obtain the porous ceramic materials. This method cannot solve the ventilation problem of dry pressing and fast firing (for example, firing periods are within 60 minutes).
CN102399090A discloses a lightweight glassy foamed ceramic, which mainly utilizes a ceramic wall, ground materials of floor tiles, and porcelain clay as raw materials. CN1028877211A discloses a foamed ceramic heat insulation plate which utilizes the polished waste of ceramic tiles, waste glass powders, waste frit powders, talcum, and red clay as raw materials. Similarly, this method cannot solve the ventilation problem of dry pressing and fast firing.
In summary, it is necessary to add clay as a component of the present formulas for making pressure-shaped and low bulk density ceramic heat insulation tiles. Because the ventilation problem of dry pressing and fast firing cannot be solved, in actual formulas the amount of foamable waste usually cannot be over 50%. If the foamable waste amount is over 80%, one has to carry out heap roasting using backing plates, the productivity is low, and the backing plates with high cost are consumed in large amounts.
In fact almost all the ceramic waste consists of residual ceramic clinker which was fired above 1200° C., which has been porcelainized, with a dense and uniform texture. As long as the problem of black cores and bulging due to the poor ventilation caused by the oxygenolysis of impurities such as organics in the polishing procedures can be solved, the low-temperature and fast firing in a roller kiln can be achieved.